1. Technical Field
The present disclosure relates to bobbins and speakers adopting the same.
2. Description of Related Art
Among the various types of loud speakers, electro-dynamic loudspeakers are most widely used because they have simple structures, good sound quality, and low costs. The electro-dynamic loudspeaker typically includes a diaphragm, a bobbin, a voice coil, a damper, a magnet, and a frame. The voice coil is an electrical conductor wrapped around the bobbin. The bobbin is connected to the diaphragm. The voice coil is placed in the magnetic field of the magnet.
To evaluate the quality of a loudspeaker, sound volume is a decisive factor. Sound volume of the loudspeaker relates to the input power of the electric signals and the conversion efficiency of the energy (e.g., the conversion efficiency of the electricity to sound). The larger the input power, the larger the conversion efficiency of the energy; the bigger the sound volume of the loudspeaker. However, when the input power is increased to certain levels, the bobbin and diaphragm could deform or even break, thereby causing audible distortion. Therefore, the strength and tensile modulus of the elements in the loudspeaker are decisive factors of a rated power of the loudspeaker. The rated power is the highest input power by which the loudspeaker can produce sound without the audible distortion. Additionally, the lighter the weight of the elements in the loudspeaker, such as the weight of the bobbin and the weight per unit area of the diaphragm; the smaller the energy required for causing the diaphragm to vibrate, the higher the energy conversion efficiency of the loudspeaker, and the higher the sound volume produced by the same input power. Thus, the strength, the tensile modulus, and the weight of the bobbin are important factors affecting the sound volume of the loudspeaker. The weight of the bobbin is related to a thickness and a density thereof. Accordingly, the higher the specific strength (e.g., strength-to-density ratio), the smaller the thickness of the bobbin of the loudspeaker, and the higher the sound volume of the loudspeaker.
However, the typical bobbin is usually made of paper, cloth, polymer, or composite material. The rated power of the conventional loudspeakers is difficult to increase partly due to the restriction of the conventional material of the bobbin. In general, the rated power of a small sized loudspeaker is only 0.3 watt (W) to 0.5 W. A thicker bobbin has a larger specific strength, but increases the weight of the bobbin. Thus, it is difficult to improve the energy conversion efficiency of the loudspeaker. To increase the rated power, the energy conversion efficiency of the loudspeaker, and sound volume, the focus is on increasing the specific strength and decreasing the weight of the bobbin.
What is needed, therefore, is to provide a bobbin with high specific strength and light weight, and a loudspeaker using the same.